Thursday, February 15, 2018

Gordon Kane Still Suffering From Severe Cognitive Dissonance

You have to be a big name in fundamental physics, like Gordon Kane, (and must have lost all sense of perspective) to have the gall to interpret evidence that the Higgs boson discovered experimentally is exactly like the one predicted by the Standard Model, to conclude that Beyond the Standard Model physics must exist right around the corner. He is, of course, full of shit, albeit in a particularly erudite fashion in this regard. His new pre-print is as follows:

Naively, the LHC Higgs boson looks like a Standard Model Higgs boson, with no guidance to physics beyond the Standard Model, as has often been remarked. The data show that what was discovered is the true Higgs boson. If one includes the full information available, experimental and theoretical, there are actually four significant clues implied by data. They point toward a supersymmetric two-doublet decoupling theory, and a hierarchy problem solution via TeV scale supersymmetry. That in turn suggests an underlying compactified string/M theory with a de Sitter vacuum, so we can be confident that the low scale model has an ultraviolet completion.

In the minimal supersymmetric world there is an upper limit on the Higgs boson mass of at most about 130 GeV, which is satisfied for the observed Higgs mass. The tree level lightest eigenstate is less than MZ and with top loop radiative corrections its mass increases up to about 130 GeV. The observed Higgs boson mass is indeed lighter than that limit.

In other words, another theory that he likes is also consistent with a Higgs boson mass of 125.09 +/- 0.24 GeV. There were about a hundred theories that made such predictions before the Higgs boson mass was known.

Also, the minimal supersymmetric model has pretty much been ruled out experimentally by the LHC. Myriad non-minimal SUSY models remain, but those models are all over the map in terms of what they predicted regarding the Higgs boson mass.

Clue 2

In a supersymmetry world with low scale superpartners the hierarchy problem is solved. That would hold here if gauginos were around the TeV scale. That is still a possible result.

Also, the direct searches for the gaugino at the LHC already exclude it in excess of 1 TeV, and any new particles at that scale would have multiple detectable indirect effects that have not been observed.

Clue 3

The well-known model [1,2] with large soft Higgs mass terms and two Higgs doublets, satisfying the electroweak symmetry breaking conditions, has one light Higgs eigenstate, two heavy neutral states, and a heavy charged pair. It automatically has decay branching ratios that are very close to the Standard Model ones, just as the data does. This is called the decoupling solution, and has been familiar for over two decades. Such a solution arises naturally in some UV complete theories, as we will briefly discuss below.

Kane is apparently not familiar with Occam's razor. When you can describe the data with both a simpler model and a much more baroque one, the simple model is preferred.

Clue 4

The fourth clue is more subtle. For a single Standard Model Higgs boson the effective Higgs potential is V = µ2h2 + λh4 . In the Standard Model λ can run to go negative at larger scales, so the potential becomes unbounded from below, and there is no resulting world. Most people reacting to this situation have shrugged and said probably the universe would be long lived so the instability can be ignored. But it was pointed out [3-7] that without vacuum stability, fluctuations in the Higgs field during inflation and in the hot early universe would have taken most of the universe into an anti-De Sitter phase, giving a massive collapse, and the expansion of the universe would never have occurred. The point was basically raised explicitly in 2008, and there was some uncertainty in how to properly calculate, over several years. Probably it was settled by the significant paper [7] in 2017. The result is that for generic expectations for the Hubble parameter during inflation, the Higgs field fluctuations generated during inflation, or the hot, high density early universe, probe the instability region, take most of the universe into the unstable AdS phase, so the usual expansion of the universe fails to occur. Thus the message is that the apparent instability is not acceptable, and new physics must arise to stabilize the vacuum. In supersymmetry λ is determined by the gauge couplings (λ = (g12 + g22)).

To restate "Clue 4" in more understandable form, you first need to understand that all physical constants in the Standard Model and kindred theories change in value in a predictable, gradual way with energy scale. In particular, the Higg potential, which gives rise to the masses of all of the fundamental particles, goes to zero or negative values at very high energies if naively extrapolated to the "GUT scale" of about 1016 GeV. This would suggest that the vacuum in the Universe is merely "metastable" rather than "stable".

Of course, we have no experimental data beyond about 104 GeV, and no data that can be reliably discerned from astronomy observations beyond about 105 GeV. So, we really don't know if the domain of applicability of the physics that we know extends up to such high energies where factors like quantum gravity could have an impact.

Kane's speculations on what happens at such high energies are just that, speculations, in areas where there are countless competing hypotheses among published physicists in the field.

For example, a far more conservative tweak to the fundamental laws of physics, asymptotic safety in quantum gravity (which also made a much more precise and accurate prediction of the Higgs boson mass based upon the same boundary conditions issues that Kane addresses in his "Clue 4" which is consistent with a "desert" of new physics before one reaches extremely high energies, can also solve the problem that he identified.

One More Thing

Needless to say, Kane also ignores the mountains of other evidence (or more precisely, the absence of evidence where evidence is expected) that disfavor his "New Physics around the corner at the TeV scale" hypothesis.